Saisei Ventures

Managing Partner Jonathan Yeh leads Saisei's investment activities. The firm discloses two additional Partners—Hikaru Saito and Sven Kili (appointed January 2025)—alongside Venture Partners James Feliciano and Toshihiko Komori (per the firm website, 2025). The partnership operates from Cambridge and Tokyo, making investment decisions as a cross-border team rather than delegating authority to a single remote office.

Saisei sources proprietary opportunities by operating directly within Japan's academic and research ecosystem rather than competing for crowded US and European syndicated rounds. The firm's Tokyo office and local network provide access to Nobel-caliber science—Japan has 22 science Nobel laureates including Dr. Shinya Yamanaka for induced pluripotent stem cells—that remains under-capitalized by Western VCs. Saisei also builds new ventures around promising academic discoveries, creating deal flow that did not previously exist as a fundable company.

Saisei's public materials describe direct equity investments and venture-creation structures rather than fund-of-funds commitments. The firm emphasizes an active company-building approach, where it enters at the seed and early stages to shape programs from proof-of-concept to the clinic. No publicly available information indicates that Saisei operates a fund-of-funds allocation or makes LP commitments to other venture firms.

The firm invests from seed through early clinical development, with a stated requirement that programs have a demonstrated path to clinical entry. Saisei describes its investment horizon as mid-term, bridging university proof-of-concept work and the investigational new drug stage where larger pharmaceutical companies typically engage. Tune Therapeutics' TUNE-401—an epigenetic therapy for hepatitis B—represents the firm's clinical-stage portfolio exposure.

Most Western biotech investors treat Japan as an occasional deal source; Saisei has built its entire investment thesis around it. The firm embeds personnel in Tokyo, sources directly from Japanese research institutions, and actively recruits operational talent to fill the leadership gaps that often prevent Japanese science from reaching global clinical trials. Saisei launched an Executive Fellows Program in April 2025 to build the management pipeline that makes this model sustainable.

Saisei concentrates on advanced therapeutic platforms, specifically cell immunotherapies, pluripotent cell replacement therapies, in vivo and ex vivo gene therapy approaches, and epigenetic editing. The firm is indication-agnostic as long as the target is a life-threatening or debilitating disease with a reasonable path to clinical and commercial manufacturing scale.

No. Saisei Ventures does not publicly disclose assets under management, fund sizes, or total deployment figures. The firm's website provides no AUM or dry-powder data, and no external financial publication has reported verified fund-raise numbers as of mid-2025.